Learn Turkish: Gelecek yıldan itibaren yıllık izin politikası değişecek. - Starting from next year, the annual leave policy will change.

The postposition itibaren (starting from / as of) always requires the preceding noun to be in the ablative case (-dan/-den). Here, yıl (year) takes -dan to become yıldan itibaren (starting from the year).

Wait, isn't gelecek the future tense suffix? How is it used as 'next' here?

You're right that -ecek/-acak is the future tense suffix (as seen in değişecek at the end of the sentence). However, the word gelecek (from the verb gelmek, meaning 'that which will come') is also used as a standalone adjective meaning 'next' or 'future'. So gelecek yıl simply means 'next year'.

Yıl appears again as yıllık. What does the -lık suffix do here?

The suffix -lık (or -lik, -luk, -lük) often creates adjectives from nouns. By adding it to yıl (year), we get yıllık, which turns the noun into the adjective 'yearly' or 'annual'.

Why does politika have the -sı suffix at the end?